Human labor is long and difficult, so it's only natural that someone be there to lend a helping hand — that's where the midwife comes in. It's not the kind of thing that's typically observed among other animals, however. Imagine the surprise of these zoologists working in southwest China when they witnessed the birth of a black snub-nose monkey whose delivery was assisted by a monkey midwife.

Normally, these high-altitude monkeys give birth at night, and the whole thing only takes about 10 to 15 minutes. Consequently, biologists have never actually seen it happen with their own eyes. But recently, Wen Xiao of Dali University in Yunnan and colleagues got lucky when they witnessed a rare day time birth. Writing in New Scientist, Michael Marshall reports:

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A female monkey gave birth to her first infant within fifteen minutes late one morning. While sitting in a rhododendron tree, she began twisting her body and calling faintly. After 10 minutes she started screaming, and then another female climbed up the tree. She was an experienced mother, and sat beside the labouring female while the crown of the infant's head appeared. Once the head was fully exposed, the "midwife" pulled the baby out with both hands and ripped open the birth membranes.

Within a minute, the mother had reclaimed the infant from the midwife, severed the umbilical cord, and begun eating the placenta. A few minutes later, the midwife went back down to the forest floor to forage.

"This is a fairly rare observation," says Sarah Turner of McGill University in Montreal, Canada, who was not involved in the Yunnan study. She says female monkeys often pull their babies out themselves, and the midwife may have adapted this behaviour. "It's hard to know what's going on in her head," says Turner, but it seems she was genuinely helping.

That could be because female black snub-nosed monkeys tend to stay in the group they were born in. As a result, the females in a group are likely to be closely related and to have strong social bonds. Animals often help their relatives because doing so preserves their own genes, a phenomenon called kin selection.

The juvenile females in the group watched the birth closely, and may have picked up a few tips. Turner says many primates remain with their groups while giving birth, giving juveniles a chance to learn.

Black snub-nose monkeys are highly social primates who live in large societies called bands. These bands, which can exceed 400 members, are sub-divided into groups of 10, mostly consisting of one male and several females. During this particular birth, two other females watched it happen — undoubtedly taking mental notes.